unfirm

from WordNet (r) 3.0 (2006)

unfirm
    adj 1: not firmly or solidly positioned; "climbing carefully up
           the unsteady ladder"; "an unfirm stance" [syn: {unfirm},
           {unsteady}]
    2: (of soil) unstable; "shifting sands"; "unfirm earth" [syn:
       {shifting}, {unfirm}]

from The Collaborative International Dictionary of English v.0.48

Unfirm \Un*firm"\, a.
   Infirm. [R.] --Dryden.
   [1913 Webster]